1. Field of the Invention
The present invention relates power supply systems including supply panels. More particularly, the present invention relates to power supply systems accessible by a variety of power users including, but not limited to, mobile systems such as vehicles and other transportation equipment. Still more particularly, the present invention relates to power supply systems configured to ensure safe use and disengagement of a power cord from the power source.
2. Description of the Prior Art
There exists a wide range of different types of transportation equipment that require, or that would benefit, from the availability of a power source from other than one or more onboard batteries that are charged by one or more engines associated with the transportation equipment. One example is a boat tied up to a dock. The boat may have a refrigerator, heater or stove, for instance, all of which require power to operate. The boat owner can choose to run the boat's engine(s) to maintain a charge on one or more batteries suitable for supplying that power. Alternatively, the boat owner can connect a power cord or cords to a shore-power source to obtain that power.
Another example of a form of transportation equipment that consumes power is a refrigerated trailer. Refrigerated trailers are widely used to transport food and other items that require temperature-controlled storage to remain viable. These trailers are hauled by tractors and when they are in motion, the trailer's refrigeration unit has an engine that generates the power to supply the refrigeration system. However, when the trailer is stopped at its destination or a way station in the course of a trip, it is still necessary to continue running the refrigeration unit's diesel motor to generate the power to keep the load temperature controlled. This process is inefficient and uneconomical. It involves the consumption of valuable fossil fuels for a vehicle that is not in motion and it unnecessarily generates harmful emissions.
At least one attempt at resolving this problem has been implemented in an experimental way. The New York State Energy Research and Development Authority (NYSERDA), in conjunction with the United States Environmental Protection Agency and the United States Department of Energy, among others, has established a project to reduce diesel consumption associated with refrigerated trailers. The project involves the provision of power sources at locations where such trailers may be at rest. The power sources are tied into existing electrical grids and are configured to allow a driver to park near the source. The source includes a power panel, a transformer to convert grid voltage to voltage levels compatible with refrigeration unit operation, and a cord extending from the panel to plug into a socket located somewhere on the trailer. These power panels may be located at truck stops, rest stops and at commercial organizations that may receive a plurality of refrigerated trailers, such as a grocery chain warehouse, for example.
There is a significant limitation associated with the proposed power panels and trailer configurations to be used for refrigeration unit power supply. The panels are designed with a power cord that must be at least long enough to reach the trailer's power socket. The power cord is electrically connected to the transformer of the panel and so it is always “live.” A concern exists with such an arrangement that the live end of the plug may contact the user, directly or indirectly, in a manner that will result in a terrible physical tragedy. Take as an example the situation where the person responsible for initiating refrigeration unit powering is standing next to the trailer near the trailer's socket on a rainy day or when the trailer is in standing water. The person must pull the live cord from a cradle on the panel and insert the plug into the trailer's socket. When powering is complete, such as when the person continues the trip to a final destination, the plug must be removed from the socket and returned to the cradle. In the course of either plugging in the cord into the socket or removing it from the socket, the person initiating engagement or disengagement of the plug can be electrocuted from an arc generated by contact with the plug. That person, as well as any other person in close proximity to the plug, could be electrocuted if the cord is dropped or left on the ground, particularly where there is standing water. Further, existing power arrangements may produce fire or electrocution caused by an electrical surge in the wiring system. Such possibilities can be avoided with a better trailer powering system.
Another similar problem that exists with the current project's power panel arrangement relates to the possibility that a person who has charged the refrigeration unit forgets to remove the power cord from the trailer's socket and drives the trailer away. Once the extent of the cord has been reached, the live cord will either be pulled out of the trailer's socket, resulting in a live wire left on the underlying surface, or the cord will be pulled out of the power panel, in which instance there could be a catastrophic failure of the panel or at least a live socket at the panel. Anyone inserting a faulty or incompatible plug into a live socket, or anyone who places any sort of object into a live socket, including individuals without any need to power a trailer refrigeration unit, may be electrocuted. Further, existing power panels having live sockets may themselves be faulty when exposed to inclement weather. All of these conditions are undesirable and should be avoided.
What is needed is a power supply system that is suitable for use with components, systems and the like in need, at least periodically, of power from a source. Such components, systems and the like may be referred to herein from time to time as mobile systems. The mobile systems include transportation or transportable equipment including, but not limited to, transportable trailers, cars, trucks, recreational vehicles, boats and ships. One type of mobile system to be discussed herein with respect to a preferred embodiment of the invention is a refrigerated trailer but, as noted, the invention is not limited thereto. What is also needed is such a power supply system that reduces the need to operate an engine or motor to supply energy to the mobile system when the mobile system is in a location where it is desirable to tap into a power grid to maintain one or more functions, such as refrigeration, for example. Further, what is needed is such a power supply system that is configured to minimize unsafe use or operation thereof.